Epidemiological investigations and multilocus sequence typing of Mycoplasma gallisepticum collected in China

Mycoplasma gallisepticum (MG) is one of the important pathogens in poultry industry and has led to major economic losses. Understanding the epidemiology is crucial to improve the control and eradication program of MG. This study collected 1,250 chicken samples, including trachea and lung, from China in 2022 to investigate the epidemiology of MG. Among the collected samples, 938 samples were positive for MG infection, resulting in an average positive rate of 75.04%. Additionally, 570 samples were positive for both MG and Mycoplasma synoviae (MS) coinfection, with an average positive rate of 45.60%. A total of 183 MG infection positive samples in this study were selected for genotyping, and the multilocus sequence typing (MLST) method based on 7 housekeeping genes was used. As a result, 183 samples belonged to 11 sequence types (STs), with ST-78 being the most prevalent. After BURST analysis, all 183 sequences were divided into group 3. Besides, 119 reference sequences from database and 183 sequences of this study were selected to construct the phylogenetic tree using the neighbor-joining method. The results revealed that the sequences from China, total 196 sequences, were classified into 4 branches. The findings suggest that the MG strains in China exhibit diverse genotypes, which may be related to international trade and the use of live vaccines. Furthermore, we detected the drug susceptibility of 10 isolated strains randomly, which may be helpful to guide the clinical use of drugs to control MG infection.